"As one of the wealthiest countries, Scotland is a net financial contributor to the EU and will remain so as an independent member.

"We have more top universities, per head, than any other member of the EU and our academics collaborate with partners across Europe. We have one of the largest national shares of Europe's total fishing grounds. The EU's fisheries policy would unravel without Scotland."

Mr Salmond argued that "not being at the top table in Europe has harmed Scotland's interests for four decades".

He added: "An independent Scotland, as an equal member state, will bring a positive, cooperative voice to the EU, in contrast to the often sullen, disengaged voices that have spoken on our behalf since Margaret Thatcher's speech in this city more than a quarter of a century ago.

"Within the UK, we are occasionally consulted. With independence, we would contribute as equals. And in contributing as equals, we would make proposals to address the democratic challenges that Europe faces today."

Living wage

Mr Salmond also warned Scotland could be "dragged out of the European Union" against its will unless it voted for independence.

He said: "The real risk to Scotland's place in the EU is not the independence referendum in September. It's the in-out referendum of 2017."

The first minister revealed he would urge the European Commission to "rethink" laws that he said prevent the Scottish government from making the Living Wage a requirement of public sector contracts.

Labour has argued that the Scottish government could get round EU rules to include Living Wage requirements in new legislation on procurement. The party secured a Scottish Parliament debate on the topic recently.

Labour MSP James Kelly said: "The Scottish government spends £10bn every year buying goods and services. These contracts should be used to ensure that every Scot is paid the Living Wage.

"400,000 Scots don't earn the Living Wage. If the Scottish government enacted our proposals - which they could do - then an average, a full-time worker who would benefit from this move would be over £2,500 a year better off."

Ahead of Mr Salmond's speech, Mr Hague wrote to the first minister, arguing that "Scotland benefits from the UK's strong voice in Europe".

Mr Hague claimed that, if Scotland opted for independence, negotiations to join the EU "are likely to be complex and long".

Scotland's independence referendum

Who? Voters in Scotland will go to the polls to vote on their country's future.

What? They will be asked the yes/no question: "Should Scotland be an independent country?"

When? The vote takes place on Thursday, 18 September, 2014.

In his letter to Mr Salmond, the foreign secretary also said the outcome "would certainly prove less advantageous than the status quo".

He said: "People in Scotland deserve to have the available facts ahead of making one of the most important political decisions in the history of our union.

"The terms of EU membership which your government has said it will seek to secure for an independent Scotland are at odds with the EU's own rules of membership."

The Scottish government has proposed using a treaty amendment under Article 48 of the Treaty of the European Union as a "suitable legal route" to facilitate an independent Scotland's membership, rather than seeking accession as a new member state.

Mr Hague said such a move would require all 28 member states to agree to this, and called on Mr Salmond to provide information on what guarantees he has received from member states regarding this.

He added: "Scotland benefits from the UK's strong voice in Europe and the UK has a proven track record in delivering for Scottish interests in the EU."

'Constructive role'

Mr Salmond sent a reply to the foreign secretary stating that "the UK government has repeatedly refused to jointly approach the Commission with the precise legal scenario on Scottish independence".

He told Mr Hague the purpose of his visit was "to articulate the constructive role an independent Scotland could play in the Europe Union".

"This contrasts of course with the renegotiation and in-out referendum favoured by your party, leading to the inevitable conclusion that the real threat to Scotland's position comes from the anti-European streak which now dominates your approach to politics," he said.

In addition to criticising Mr Salmond's stance on Europe, Mr Hague said Scotland's first minister had made a "gross error of judgement in international relations" by paying tribute to Russia at a time when it was "annexing by force the Crimea".

Mr Hague was reacting to remarks by the SNP leader which are part of a wide-ranging interview to be published in GQ magazine on 1 May.

Asked about whether he admired Mr Putin, Mr Salmond is reported to have said: "Certain aspects. He's restored a substantial part of Russian pride and that must be a good thing.

"There are aspects of Russian constitutionality and the inter-mesh with business and politics that are obviously difficult to admire. Russians are fantastic people, incidentally, they are lovely people."